This is a proposal with the long-term objective of understanding the regulation of glycosylation in lymphoid cells in order to further understanding the importance of this essential cellular process for the secretion of immunoglobulin and for the insertion of antigen receptors in the plasma membranes of these cells. Current goals are to establish the importance or role of nucleotide pyrophosphatase for the regulation of glycosylation and to define the phenotypic results in lymphoid cells which have elevated levels of this enzyme and associated changes in glycosylation. Specifically, studies are designed to define phenotypic differences in MOPC 315 wild-type and 315 variant plasmacytomas with high specific activities of this enzyme. Glycosylation and oligosaccharides processing of the immunoglobulin heavy chains will be studied to determine the exact mechanism(s) for the underglycosylation of immunoglobulin in the 315 variant cells with elevated levels of nucleotide pyrophosphatase. The structures of asparagine-linked oligosaccharides from cell membrane glycoprotein will be characterized in these cell lines to determine if alterations in glycosylation involve proteins other than immunoglobulins. In addition, baseline activity of the pyrophosphatase will be determined in a number of different lymphoid cell lines and tissues and correlated with glycoprotein synthesis. In all cases, this enzyme also will be measured under experimental conditions known to modulate its activity. Finally, the role of nucleotide pyrophosphatase for the regulation of glycoconjugate precursors will be studied by defining it interaction with nucleotide sugars in the rough endoplasmic reticulum and by determining its importance in glycosaminglycan metabolism. These studies are designed to generated new insights on the regulation of glycosylation. Potentially they have an even broader significance since they will begin to characterize an important event in the immune response. An understanding of the regulation of glycosylation in lymphoid cells will provide basic information on the mechanism of the initiation of the immune response since the antigenic stimulation of lymphocytes to differentiate into plasma cells subsequently involves the synthesis of large amount of glycosylated immunoglobulin. This knowledge may be major significance for the understanding of the basic molecular defects in certain hereditary immunodeficiency diseases, autoimmune disorders, and malignancies.